1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof, and particularly relates to a method for bonding a semiconductor element.
2. Description of the Background Art
In view of stricter environmental regulations in recent years, a demand for environmentally friendly electronic devices (i.e., electronic devices corresponding to high quality, high efficiency, and energy saving) has been growing. Particularly, an electronic device corresponding to high power has been demanded as with industrial equipment, a drive control device for a home electric appliance provided with a motor, an in-vehicle control device for an electric vehicle and a hybrid vehicle, a control device for a railway vehicle, a control device for solar power generation, and the like. Further, high efficiency and low loss in the operation under a high-load environment (under a high-temperature environment) of electronic devices have been demanded. The high-temperature environment is an environment at a temperature of 150 to 175° C. or higher (e.g., 200° C.). Development of a semiconductor element which operates under the high-temperature environment has been progressing. Also, a high density in current has been promoted as a characteristic of a package.
Energy saving performance under a high-temperature environment has been demanded for an electronic device used, in particular, as an in-vehicle control device and a control device for a railway vehicle. The normal operating temperature has been, for example, 150° C. or lower. However, a demand for use under a high-temperature environment of 200° C. or higher is deemed to increase. Under a high-temperature environment of 200° C. or higher, SiC or GaN can well correspond, instead of Si, as a semiconductor element.
In view of this, it has been necessary to review materials and structures of electronic devices in order to suppress a switching loss and realize a low loss and high efficiency in operation under the high-temperature environment. Particularly, since a bonding portion inside a semiconductor device applied to an electronic device is most susceptible to deterioration, realizing high quality, high reliability, and long life of the bonding portion has been a large problem.
Then, to enhance high-temperature durability of the bonding portion, a bonding material having sinterability has been used instead of a solder material (e.g., see Japanese Patent Application Laid-Open No. 2004-107728). When a semiconductor element is bonded to a substrate with a bonding material having sinterability, the bonding material is sintered by pressurizing and at the same time heating the bonding material between a rear surface of the semiconductor element and a front surface of the substrate, and thus bonding is performed.
As described above, when the bonding is performed with the bonding material having sinterability, for example, the bonding material is pressurized between the rear surface of the semiconductor element and the front surface of the substrate in addition to heating. As a result, there has been a case where sintering is performed while the bonding material is protruded around the semiconductor element by pressurization. The protruded bonding material is sintered without being sufficiently pressurized. The bonding material which has been sintered while being protruded easily drops off because a fillet shape is not formed as in the case of the solder material. As a result, there has been such a problem that in a manufacturing step subsequent to a step for bonding the semiconductor element, the protruded bonding material drops off by vibrations or the like, which causes a trouble such as a short-circuit.